Conventionally, there are known micromachine switches which use the piezoelectric effect (e.g., Patent Document 1) or which use both the piezoelectric effect and the electrostatic effect (e.g., Patent Document 2).
With reference to FIG. 30, a micromachine switch using the piezoelectric effect will be described in detail. FIG. 30 is a perspective view showing the micromachine switch using the piezoelectric effect. In FIG. 30, the micromachine switch comprises: a signal line conductor 2 and earth conductors 3 formed on a substrate 1; a drive shunt mechanism 7 for blocking a passage of a high-frequency signal; and a support 8 provided between the drive shunt mechanism 7 and one of the earth conductors 3. The drive shunt mechanism 7 comprises: a conductive layer 4; a piezoelectric body 5 which is drive means for displacing the drive shunt mechanism 7 when being provided with a control signal; and an elastic body 6. In the case of blocking the high-frequency signal (i.e., in the case of turning off the switch), a voltage is applied to the piezoelectric body 5 as a control signal. As a result, the drive shunt mechanism 7 is displaced downward, and the conductive layer 4 contacts the signal line conductor 2 and the other one of the earth conductors 3. Consequently, the signal line conductor 2 is electrically connected to the other one of the earth conductors 3 via the conductive layer 4, whereby the high-frequency signal is blocked. In the case of passing the high-frequency signal (i.e., in the case of turning on the switch), the application of the voltage to the piezoelectric body 5 is ceased. As a result, the drive shunt mechanism 7 returns to its original state, and the electrical connection between the signal line conductor 2 and the other one of the earth conductors 3 is disconnected, whereby the high-frequency signal passes through the signal line conductor 2.
A micromachine switch using both the piezoelectric effect and the electrostatic effect will be described in detail with reference to FIG. 31. FIG. 31 is a perspective view showing the micromachine switch using both the piezoelectric effect and the electrostatic effect. In FIG. 31, the micromachine switch comprises: an insulated substrate 11; a drive arm 12 provided on the substrate 11; electrostatic electrodes 13 which are respectively provided on the substrate 11 and at a lower surface of the drive arm 12 so as to face each other; first applying means (not shown) for applying a voltage to the electrostatic electrodes 13; a piezoelectric drive electrode 16 provided on an upper surface of the drive arm 12; second applying means (not shown) for applying a voltage to the piezoelectric drive electrode 16; a connection electrode 17 provided at the lower surface of the drive arm 12; and terminal electrodes 18 provided on the substrate 11. The piezoelectric drive electrode 16 has a piezoelectric body layer 14 and two electrodes 15 respectively provided at upper and lower surfaces of the piezoelectric body layer 14. In the case of turning on the switch, voltages are applied to the electrostatic electrodes 13 and to the piezoelectric drive electrode 16 by the first and second applying means. This causes the drive arm 12 to be displaced downward, whereby the connection electrode 17 contacts the terminal electrodes 18. As a result, the terminal electrodes 18 are electrically connected to each other via the connection electrode 17, and a high-frequency signal passes through the terminal electrodes 18 via the connection electrode 17. In the case of turning off the switch, the application of the voltages to the electrostatic electrodes 13 and to the piezoelectric drive electrode 16 is ceased. This causes the drive arm 12 to return to its original state, whereby the electrical connection between the terminal electrodes 18 is disconnected and the high-frequency signal is blocked.    [Patent Document 1] Japanese Laid-Open Patent Publication No. 2003-217421    [Patent Document 2] Japanese Laid-Open Patent Publication No. 2005-302711